Bidirectional stepping mechanism

ABSTRACT

A disclike camming wheel has a pattern of intersecting grooves cut in one face thereof. A lever-operated pin, biased to a center position within one of the grooves, is operated radially of the disc face in such a manner that when the pin is moved outwardly from the axis of rotation, the cam wheel is rotated in the opposite direction. The depth of tee grooves is varied such that a detent action is achieved to hold the cam wheel in a fixed position.

United States Patent Inventors Salvatore J. Magri Sunnyvale; John E. Nidecker, Menlo Park. both of, Calif. Appl. No. 826,609 Filed May 21, 1969 Patented July 6, 1971 Assignee Hewlett-Packard Company Palo Alto, Calif.

BIDIRECTIONAL STEPPING MECHANISM 10 Claims, 5 Drawing Figs.

0.8. CI 74/88 Int. Cl Fl6h 27/02 Field of Search 74/88 [56] References Cited UNITED STATES PATENTS 630,830 8/1899 Houghton 74/88 Primary Examiner-Milton Kaufman Attorney-Roland I. Griffin ABSTRACT: A disclike camming wheel has a pattern ofintersecting grooves cut in one face thereof. A lever-operated pin, biased to a center position within one of the grooves, is operated radially of the disc face in such a manner that when the pin is moved outwardly from the axis of rotation, the cam wheel is rotated in the opposite direction. The depth of tee grooves is varied such that a detent action is achieved to hold the cam wheel in a fixed position.

BIDIRECTIONAL STEPPING MECHANISM BACKGROUND OF THE INVENTION In many instrument and other applications it is desirable to operate a cam in a rotary manner in either of two senses of rotation under the control of a finger actuated lever. The cam in turn may operate a paper roller or other rotary mechanism. Whatever the application, the cam should be rotatable in either direction and positively held in each rotary position by a detent or other locking mechanism once the desired rotation is completed.

In the past, mechanisms capable of performing this function have required relatively complex gearing and precision machined parts. Some have used ratchetlike levers which are somewhat fragile and easily broken. Others have been difficult to lock in a particular rotary position.

It is, therefore, an object of this invention to provide an improved two-way rotary drive mechanism which is relatively simple in construction.

Another object of this invention is to provide an improved bidirectional lever operated cam.

BRIEF DESCRIPTION OF THE INVENTION In a preferred embodiment of this invention a bidirectional stepping mechanism converts a lineal lever motion into a rotary motion. The mechanism includes a disclike cam member having an axis of rotation and mounted for rotation about such axis. The cam member has a face substantially perpendicular to the axis of rotation. First and second sets of grooved track segments are formed in the face of the cam member. Each track segment of the first set intersects with a different track segment of the second set. Furthermore, each track segment of the first set interconnects at either end with one end of a 7 different track segment of the second set. Finally, a pin BRIEF DESCRIPTION OF THE DRAWINGS The novel features that are considered characteristic of this invention are set forth with particularity in the appended claims. The invention, itself, however, both as to its organization and method of operation, as well as additional objects and advantages thereof will best be understood from the following description when read in connection with the accompanying drawings, in which:

FIG. 1 is a plan view of the face of a bidirectional stepping mechanism constructed in accordance with this invention;

FIG. 2 is a side view of the stepping mechanism illustrated in FIG. 1;

FIG. 3 is a partially cutaway elevation view of the stepping mechanism illustrated in FIG. 1;

FIG. 4 is a partial cross-sectional view taken along the section line 4-4 of FIG. 1 illustrating the configuration of one of the track segments in the cam face; and

FIG. 5 is a partial cross-sectional view taken along the section line 5-5 of FIG. 1 illustrating the configuration of the one second set of track segments.

DESCRIPTION OF THE INVENTION of the housing 14 as by screws 18. Also fixedly secured to the axle is a disclike cam member 10. A torsion spring 22 is rotatably fitted over the axle 20. The free ends of the torsion spring 22 rest against a preload pin. 24 which is adjustably secured as noted by the arrows 25 to the end plate I6. This maintains the torsion spring under load and serves to position the torsion spring ends to maintain a lever 26 biased to a predetermined center position as illustrated. The lever 26 is pivotally mounted as by a screw 32 to the end of the housing 14 immediately adjacent the cam 10.. The exposed end 28 of the lever 26 provides a flat finger button which may be raised or lowered as by a person's fingers. The other end of the lever 26 is Z-shaped and at the extreme end mounts a pin 34 which, as will be described, engages grooved tracks formed in the face 31 of the cam 10. The Z-shaped positions the pin 34 to operate generally radially of the face of the cam 10. Preferably the Z-shaped portion of the lever 26 is formed of a flexible material to permit the pin 34 to flex along the axle 20 and thereby track the bottom of the track segments as will be described. The pin 34 is biased against the face of the cam 10.

The face of the cam has formed therein a first set of arcuate grooved track segments 36 which are symmetrically disposed about the axle 20 (the axis of rotation of the cam 10). Additionally, a second set of grooved arcuate track segments 38 are formed in the face 3ll of the cam 10 with each track segmerit of the second set intersecting a different track segment 36 of the first set. Furthermore, each end of each track segment of the first set interconnects with one end of a different track segment of the second set. In this manner, a completely symmetrical interlocking, intersecting pattern, symmetrical about the axle 20 is formed.

In a particular embodiment that was constructed and is preferred, the second set of grooved track segments 38 are formed, when a cam 10 having a diameter of 1.2 inches is used, to have a radius of 0.940 inches with the center point being taken from the pivot axis 32 of the lever arm. In this manner, the pin 34 of the lever is free to move in the particular track 38 in which it is engaged without resistance from the sides of the track segments as will be described hereinafter. Each track segment 36 of the first set is formed on an arc having a radius of 0.250 inches drawn from a centerline lying on a radius of0.3 10 inches from the axis of rotation of the cam 10.

Further in accordance with this invention, each of the track segments 36 and 38 is formed in varying depths to positively control the manner of movement of the pin 34 through the tracks when actuated by the lever 26. Specifically, each of the first set of grooved track segments 36 has a depth profile, as may be seen in the partially cutaway viewing of FIG. 4, to have a low point 4%), i.e., the point of maximum track depth, at roughly the center portion of the track, with the track depth decreasing in either direction from the low point 40 until the track segment intersects the ends of the adjoining track segments 38. In contradistinction, each of the track segments 38, as may be seen in the depth profile of FIG. 5, has a low point 42 at either end of each segment with the track depth decreasing toward the center portion of each track segment to the point of intersection with the track segments 36. This creates a stepped portion 44 at either of the ends of the track segment 36 (FIG. 4). It will be recalled that the pin 34 is biased against the bottom of the track segments by the lever 26. Actually the Z-shaped portion of the lever may be flexible for this purpose. Alternatively the entire lever assembly may be springloaded to bias the pin 34 against the face of the cam 10. The purpose of these stepped portions 44 will become apparent from a description of the operation of the bidirectional stepping mechanism.

As was described, the lever 26 is biased to a central position by the torsion spring 22. If now, one depresses the lever 26 downward in the drawing, as denoted by the arrow 46, the pin 34 at the bottom of the track segment 36 as illustrated in FIGS. I and 5 cannot move directly along track segment 38 since track segment 36 is depressed. The force of the pin 34 against the sides of track segment 36 causes the cam I0 to move in a clockwise sense permitting the pin 34 to move outwardly of the cam through the track segment 36, i.e., to the left in FIG. 4, until the pin 34 slips over the step 44 into the lower or deeper end portion of the adjoining track segment 38. The lever is now released and the force provided by the torsion spring 22 returns the lever to its center position at the same time driving the pin 34 back from the low point 42, illustrated at the right-hand portion of the track 38 of FIG. 5, up the ramp formed by the bottom of the track segment 38 until the pin 34 slips over into the end of the lower track 36 of FIG. at which it is at the neutral or center position illustrated in FIG. 1. The return movement of the pin 34 is facilitated by the fact that the center of curvature of the track 38 coincides with the center of rotation of the lever 26 holding the pin 34.

It will be observed that with the pin 34 back in its rest position and also lying at the low point 40 of the track segment 36, the cam is held so that the pin functions as a detent and holds the cam at this one particular rotational position. Furthermore, it is seen that during the movement of the pin 34 driving the cam in its clockwise rotation that the motion of the cam 10 is at all times positive. At no time is the cam required to operates on its own without a force being applied thereto. The pin 34 is at all times acting against the outside wall of one of the track segments 36.

If it is desired to rotate the cam in a counterclockwise direction, the end 28 of the lever 26 is lifted as denoted by the arrow 48 in FIG. 1. This causes the pin 34 to move downwardly in FIG. 1 (to the right in the cross-sectional illustration of FIG. 4) from the low point 40 of the track 36 up over the right-hand step 44 onto the lower end portion of the adjoining track segment 38. Now as the lever is released, the pin returns to its center position under the influence of the torsion spring. During this movement, the pin 34 moves from the low portion of the track 42 (the lefthand side of the drawing of FIG. 5) up the track until it is allowed to slip over the step into the lower central portion of the track 36 illustrated in FIG. 5. Here again the camming operation provided by the pin 34 which causes thecounterclockwise rotation is positive at all times. Further the detent action of the cam provided by the pin resting at the low portion of the track 36 still prevails. The return of the pin 34 under the influence of the spring 22 is facilitated since the centers of curvature of the pin motion and the track segments 38 coincide. Hence there is no motion of the cam, i.e., the roller, during the return stroke ofthe pin 34.

There has thus been described a relatively simple bidirectional stepping mechanism which is of relatively low cost to manufacture and yet relatively trouble free.

It will be obvious that various modifications may be made in the apparatus and in the manner of operating it. It is intended to cover such modifications and changes as would occur to those skilled in the art, as far as the following claims permit and as far as consistent with the state of the prior art.

What we claim is:

1. A stepping mechanism for converting lineal motion into rotary motion comprising:

a disclike cam member having an axis of rotation and mounted for rotation about said axis;

said cam member having a face substantially perpendicular to said axis of rotation with first and second sets of grooved track segments formed therein;

each track segments of said first set intersecting a different track segment of said second set;

each segment of said first set interconnecting at either end with one end of a different track segment of said second set;

a pin adapted to ride in said grooved track segments,

thereby to impart rotary motion to said cam member when operated in the plane of said cam face;

spring bias means for spring biasing said pin to a radial position on said cam face corresponding to any of the intersections of track segments of said first set with track segments of said second set; and

means connected to said pin for imparting generally radial movement to said pin in a first direction causing said pin to traverse one of said first set of track segments to the interconnection with an adjoining one of said second set of track segments and thereby causing rotation of said cam member in a first sense, said spring bias means returning said pin to said radial position along said adjoining one of said second set of track segments.

2. A mechanism according to claim 1 wherein said pin movement imparting means imparts generally radial movement to said pin in a second substantially opposite direction causing said pin to traverse one of said first set of track segments to the interconnection with an adjoining one of said second set of track segments and thereby causing rotation of said cam member in a second sense opposite said first sense, said spring bias means returning said pin to said radial position along said adjoining one of said second set of track segments.

3. A mechanism in accordance with claim 1 wherein said pin is biased to ride against the bottom of said grooved track segments.

4. A mechaniam in accordance with claim 3 wherein the depth of each track segment of said first set decreases linearly as a function of the distance from the intersection with a track segment of said second set, whereby said pin serves as a detent for said cam member and the depth of each track segment of said'second set increases linearly as a function of the distance from each said intersection, the depth of each track segment of said second set at each said intersection being less than that of each track segment of said first set, thereby to separate each track segment of the respective sets by a stepped portion.

5. A mechanism in accordance with claim 4 wherein said pin movement imparting means imparts generally radial movement to said pin in a second substantially opposite direction causing said pin to traverse one of said first set of track segments to the interconnection with an adjoining one of said second set of track segments and thereby causing rotation of said cam member in a second sense opposite said first sense, said spring bias means returning said pin to said radial position along said adjoining one of said second set of track segments.

6. A mechanism in accordance with claim 5 wherein each of said tracks has substantially the same maximum depths.

7. A mechanism according to claim 6 wherein said pin movement imparting means includes a lever arm pivotally mounted to pivot about a second axis parallel to said axis of rotation, said pin being mounted in one end of said lever arm at a predetermined distance from the pivotal mounting point, each of said second set of track segments having a radius equal to said predetermined distance, thereby to facilitate the return of said pin to said radial position.

8. A mechanism according to claim 7 wherein each of said first set of track segments has a radius less than said predetermined distance.

9. A mechanism according to claim 1 wherein said track segments form a symmetrical pattern about said axis.

10. A mechanism in accordance with claim 1 wherein each of said first set of track segments has a first arcuate configuration and each of said second set of track segments has a second arcuate configuration different than said first configuration. 

1. A stepping mechanism for converting lineal motion into rotary motion comprising: a disclike cam member having an axis of rotation and mounted for rotation about said axis; said cam member having a face substantially perpendicular to said axis of rotation with first and second sets of grooved track segments formed therein; each track segments of said first set intersecting a different track segment of said second set; each segment of said first set interconnecting at either end with one end of a different track segment of said second set; a pin adapted to ride in said grooved track segments, thereby to impart rotary motion to said cam member when operated in the plane of said cam face; spring bias means for spring biasing said pin to a radial position on said cam face corresponding to any of the intersections of track segments of said first set with track segments of said second set; and means connected to said pin for imparting generally radial movement to said pin in a first direction causing said pin to traverse one of said first set of track segments to the interconnection with an adjoining one of said second set of track segments and thereby causing rotation of said cam member in a first sense, said spring bias means returning said pin to said radial position along said adjoining one of said second set of track segments.
 2. A mechanism according to claim 1 wherein said pin movement imparting means imparts generally radial movement to said pin in a second substantially opposite direction causing said pin to traverse one of said first set of track segments to the interconnection with an adjoining one of said second set of track segments and thereby causing rotation of said cam member in a second sense opposite said first sense, said spring bias means returning said pin to said radial position along said adjoining one of said second set of track segments.
 3. A mechanism in accordance with claim 1 wherein said pin is biased to ride against the bottom of said grooved track segments.
 4. A mechaniam in accordance with claim 3 wherein the depth of each track segment of said first set decreases linearly as a function of the distance from the intersection with a track segment of said second set, whereby said pin serves as a detent for said cam member and the depth of each track segment of said second set increases linearly as a function of the distance from each said intersection, the depth of each track segment of said second set at each said intersection being less than that of each track segment of said first set, thereby to separate each track segment of the respective sets by a stepped portion.
 5. A mechanism in accordance with claim 4 wherein said pin movement imparting means imparts generally radial movement to said pin in a second substantially opposite direction causing said pin to traverse one of said first set of track segments to the interconnection with an adjoining one of said second set of track segments and thereby causing rotation of said cam member in a second sense opposite said first sense, said spring bias means returning said pin to said radial position along said adjoining one of said second set of track segments.
 6. A mechanism in accordance with claim 5 wherein each of said tracks has substantially the same maximum depths.
 7. A mechanism according to claim 6 wherein said pin movement imparting means includes a lever arm pivotally mounted to pivot about a second axis parallel to said axis of rotation, said pin being mounted in one end of said lever arm at a predetermined distance from the pivotal mounting point, each of said second set of track segments having a radius equal to said predetermined distance, thereby to facilitate the return of said pin to said radial position.
 8. A mechanism according to claim 7 wherein each of said first set of track segments has a radius less than said predetermined distance.
 9. A mechanism according to claim 1 wherein said track segments form a symMetrical pattern about said axis.
 10. A mechanism in accordance with claim 1 wherein each of said first set of track segments has a first arcuate configuration and each of said second set of track segments has a second arcuate configuration different than said first configuration. 